二者的基本用法一样
1) Be certain 如：Manchester are certain/sure to win.(The other team haven’t got a chance.)曼彻斯特队肯定会赢。(另一队连一点希望都没有)
2) Before the game stared, Alan felt quite sure/certain of winning, but after the first five minutes he began to lose confidence. 比赛开始前，艾伦感到很有把握赢，但比赛了5分钟后他开始失去信心了。